Research On Ion Beam Cleaning Technology Of KDP Crystal

KH2PO4(referred to as KDP)is a kind of nonlinear optical crystal with excellent optical properties,and it plays an extremely important role in the field of ICF.Because of the soft texture of KDP crystal,and it is susceptible to pollution,and impurity elements are usually trace,the effect of commonly used cleaning method is poorer,and the improper operation will damage the processed surface.So according to the above problems,introducing the ion beam polishing technology into the cleaning process of KDP crystal,to build a complete process chain of the ultra-precision machining of KDP crystal.This paper has taken the following several aspects studies.(1)The model of temperature field of KDP crystal under ion beam bombardment was established.Software named TRIM was used to simulate the interaction between Ar+ and optical surface.And the distribution and energy deposited into optical element,The influence of ion energy and incidence angle on the deposited energy,the disturbance layer was analyzed.According to deposited energy distribution in the surface,the energy power distribution model under the arbitrary incidence angle was established.Based on the theory of heat transfer and energy distribution model,the temperature field under mobile Gaussian plane heat source model was established.(2)The optimization of technological parameter of ion beam cleaning KDP crystal were studied.The theoretical model was verified by ANSYS.The influence of movement speed on the peak temperature was studied,and obtained the optimal speed which can lower the peak temperature and ensure the removal efficiency at the same time.The parameters were optimized through orthogonal experiment,the influence of various parameters on the peak temperature and peak temperature weight influence weight were analyzed.(3)The parameters of processing between simulation matching.The beam parameters under different parameters were collected by Faraday cup,and the influence of processing parameters(beam voltage,beam current and target distance,etc.)on the simulation parameters(beam distribution parameters,peak beam density,etc.)was analyzed.Optimizing processing parameters by comparing the peak temperature under various combination of voltage and beam current.The feasibility of ion beam cleaning large diameter KDP crystal was verified by using the optimized processing parameters.(4)The experiment of IBF for KDP crystal were studied.After comparing different cleaning processes of KDP crystal microstructure,the excellent cleaning effect of IBF was verified.The removal function model was verified by comparing the theoretical removal efficiency with the actual machining removal efficiency.It shows that ion beam cleaning will not damage or further reduce the roughness of KDP crystal by comparing the surface roughness under different removal depths.The surface element detection of different ion beam cleaning process of KDP crystal was analyzed by using TOF-SIMS,it shows that IBF has the capability of remove impurities,and also doesn't introduce additional impurities at the same time.